After Facebook signs a user in, what login name to store in the app's DB?

After Facebook signs in for a user, what is a proper Login name and email to use to store this user into the app's Database?

Is there any do开发者_StackOverflowcs on it? I haven't seen any yet. Is it the same for new JS SDK and old JS SDK?

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every user would have a unique facebook user id number that is probably what your looking for